A continuous need exists for fertility control for providing freedom for women to choose when they want to have children. Efforts were made, in the early 1960's, to satisfy the need for fertility control with the introduction of the oral contraceptive pill comprising an estrogenic steroid and a progestational steroid. The contraceptive pill used by the prior art comprises a tablet form that delivers the steroids in a bulk, nonrate, uncontrolled dose. In one prior art contraceptive regimen, a tablet comprising both an estrogen and a progestin are administered for about three weeks, while in another modification a tablet comprising an estrogen is administered for about two weeks and a tablet comprising an estrogen and progestin are administered for about a week. The contraceptive steroids were delivered as an oral tablet devoid of rate-controlled delivery properties because the contraceptive steroids are practically insoluble in aqueous fluids and, accordingly, they do not lend themselves for manufacture into a dosage form that administers the steroids at a controlled and known rate per unit time.
The contraceptive steroids, moreover, were delivered by the prior art in a dose unprotected from the changing environment of the gastrointestinal tract, with little consideration for the steroid's pharmacological and physiological effects and the accompanying disadvantages on a recipient. For example, one disadvantage associated with the prior art tablet accompanies the dose-dumping of estrogen which can lead to gastrointestinal disturbances, nausea, weight-gain, edema, and an increase in the incidence of thrombophelibitis and associated cardiovascular disorders. Also, the prior art tablet does not provide for the fast release of a progestational steroid for avoiding liver metabolism of the steroid and the subsequent delivery of an estrogen in small continuous doses for lessening the incidence of side effects in the recipient. The oral contraceptives are disclosed in The Pharmacological Basis of Therapeutics, by Goodman and Gilman, 7th Ed., pages 1430 to 1439 (1985), published by Macmillian Publishing Company.